Stylus for sound-reproducing machines



Dec. 31, 1929. a. F. TAYLOR 1,741,256

STYLUS FOR SOUND REPRODUCING MACHINES Filed Feb. 17. 1928 Inventor: I George F. Taylor, y .v r

His Attorney Patented ec, 31, 192a UN TE STATES PATENT-OFFICE.

u enonen r. TAYLOR, or scnmncmnx, NEW. ionic, ASSIGNOB TO GENERAL nnnc'rnrc comm, a-coarom'rron or new Yonx smus IOR sotmn anraonuome mcnnms Application flledlebruary.17,192$; Serial m. 25t,145.

'- Present invention relatesto styli or needles for sound reproducing devices.

. Heretofore such needles have. generally been made from fiber, steel or tungsten. The use of'fiber'or steel for this purpose has been somewhat objectionable however, due to the i fact that these materials wear 'away relatively quickly and thereby cause injury to the record which is being reproduced. Although the pointof a tungsten needle will wear for a longer period ottime-than the point on a] fiber or steel needle the tungsten needle has certain-limitations, For example, tungsten needleswhen examined under the microscope are seen to be composed of fibers havingsharp pointed ends which cut into and in'ure' a v.record until'the fibers. become roun ed by wear against it.' When employed with a record the needle is inclined at an angle to it.

After the tungsten point on the needle has worn away slightly, the, steel shank will ride on the record and ultimately cause its dee structi on unless the needle isrenewed.

Accordingto the present invention I have provided a metallic needle which will play a very large number of records without'showing any appreciable wear, the point of the needle having a hardness comparable with that of a diamond. The improved needlereproduces records with great fidelity and without causing any injury to them.

-In carrying-out the invention I employ a' com osition consisting. largely of an element, of t 1e sixth group of Mendelejeifs periodic 7 table, such astungsten or-molybdenumbut containing carbon and an'element of the iron group, such as cobalt, iron, nickel or a'mixture' of these latter elements. The cobalt or iron group. content mayvary from about 3 to 25 per cent of the total content of the com positign, the carbon from about 3 to 10 per e cent, while the tungsten constitutesthe re- "mainder of the composition. .1 have obtained I per cent carbon audit-bout 81.8 per centtungparticularly good results with needles cone sisting of about 1'3 1 per cent cobalt, about 5.2

sten.

a "The needles may be formed in various ways, for example, the materials employed may be mixed with a suitable binder and pressed asbefore.

extruded in theiorm o f a thinwire' and needlethen ground'to the desired shape;

When the needles are extruded I mix powdered tungsten, cobalt and rbon in the above proportions with an organ-1c binder, for example ordinary flour,- the amount of flour employed being equal to about 1% to 2 per cent of the total mixture; The flour 'is moistened with water and a small amount of'sodium hydroxide to provide an. alkaline paste. The mixed materials are placedin an ex- 'truding machine and pressure applied thereto. The opening in the extruding machine is Y somewhat larger than the diameter of a needle in its final form in order to allow' for shrinkage of the needle when laterheated.

The extruded material, which is in the form ofa thin wire, is allowed to dry and becomes quite hard so that it may be handled easily and broken into desired lengths. The wire thus formed is embedded in alumina powder,

placed in a graphite cylinder, and fired in a hydrogen furnace atja temperature of about 1400 G. At this temperature the wires or rods become sintered into hard steel-like forms. These forms are cut into desired lengths and ground so as to have sharp pointed ends. After the needle has been ground,

to approximately the desired shape, diamond dust ma be advantageously employed in the; final grinding step, When ground in this way, the needles will have a ver point when examined under the mlcroscope.

Instead of mixing the powdered elements as above described tungsten carbide may be smooth I formed and then powdered and mixed with powdered cobalt and flour and sintered and 'If' desired the needle may be formed approximately to size by placing the powdered elements, tungsten, carbon and cobalt; or tungsten carbide and cobalt in a heat resistant mold, such as carbon, heating them to I the sintering temperature of the mixed powders and simultaneously applying pressure thereto as described in the copen'ding applications of Samuel L. Hoyt, Ser. No. 181,536, and Emery G. Gilson, Ser. No. 187,328, filed April 6, 1927, and April 28, 1927, respectively and assigned to the assignee of the present application. When'the needle is formed in this manner one of the electrodes employed in pressing the materials may be a refractory J'metal member such as tungsten which ispressed into the powdered mixture and firmly secured thereto to form a part of the needle. The needle may then be ground to the proper slze.

It is not necessary however to form the pressed material to approximately the shape of the needle. The powdered materials may be formed in small pieces according to the processes outlined in the above applications and then silver soldered to-a steel or, other metal shank and ground to the desired form.

It has been my ex erience that the best needles are produced rom the powdered matetungsten carbide.

rials which are hot pressed according to the method disclosed inthe above Hoyt and Gilson patent application. Although the best needles have been formed from a composition consisting of tungsten, carbon and cobalt, satisfactory needles have also been obtained by employing a material consisting entirely of In the drawin forming a part of the present application Tig. 1 represents the sound box of a sound reproducing device provided with my improved form in engagement with record or tablet 5 inwhich the sound record is in the form of an undula tory"'=-groove arranged spirally on the faceof the tablet.

The well known form of tungsten needle comprises a steel shank 6 and a tungsten point 7 secured in a suitable manner to the shank,

point 8 is either silver soldered to a steel or other suitable metal shank 9 or secured thereto during the pressin and sintering operation as above describei What I claim as new and desire to secure by Letters Patent of the United States, is,-

1. A stylus for sound reproducing machines, said stylus having a record engaging tip consisting mainly of an element of the sixth group of Mendelejefis periodic table but eontaining an appreciable amount of carbon and an element of the iron group.

'2. A stylus for sound reproducing machines, said stylus having a record engaging, tip consisting largely of tungsten but containing an appreciable amount ofcarbon and an element of the iron group.

3. -A' stylus for sound reproducing machines, said st lus having a record engaging tip consisting largely of tungsten but contain- 4.. A stylus for sound reproducing machines, said stylus having a record engaging tip consisting largely of tungsten but containing carbon and from 3 to 25 per cent of cobalt.

5. A stylus for sound reproducing machines, said stylus having a record engaging tip consisting largely of tungsten but containing about 3 to 10per'cent carbon and from 3 to 25 per cent of cobalt.

ing appreciable amounts of carbon and'co-= 6. A stylus for sound reproducing machines, said stylus having a record engaging tip consisting largely of tungsten but contain ing about 5 per cent carbon and an element of the iron group.

7. A stylus for sound reproducing machines, said stylus having a record engaging" tip consisting of a sintered composition consisting largely of tungsten but containing an appreciable amount of carbon.

8. A st lus having a tipportion consisting largely o tungsten-carbide but containing an appreciable amount of cobalt. 1

9. A stylus having a tip portion consistin mainly of a carbide of an element of the sixth group of Mendelejeifs eriodic table and an appreciable 7 amount 0 group. A

In witness whereof, I have hereunto set my hand this 16th day of February, 1928.

GEORGE F. TAYLOR.

as indicated in Fig. 2. It will be seen thatas the needle is inclined at an angle to the record any appreciable wear on the tungsten point will bring the steel portion of the shank into contact with the record.

The improved formof needle may consist entirely of a sintered mixture of tungsten, carbon and cobalt, as indicated-in Fig. 3, or, if desired, only the record engaging tip of the needle may consist of the sintered material.

as indicated in'Fig.-4. In the latter case the metal of the iron 

